Patch #403947: On Cygwin, use the Unix compiler class, and not

the Cygwin-specific compiler class.

 (According to Jason Tishler, cygwinccompiler needs some work to
  handle the differences in Cygwin- and MSVC-Python. Makefile and
  config files are currently ignored by cygwinccompiler, as it was
  written to support cygwin for extensions which are intended to be
  used with the standard MSVC built Python.)

Lib/distutils/ccompiler.py

@@ -842,7 +842,10 @@ class CCompiler:
 _default_compilers = (
 
     # Platform string mappings
-    ('cygwin.*', 'cygwin'),
+
+    # on a cygwin built python we can use gcc like an ordinary UNIXish
+    # compiler
+    ('cygwin.*', 'unix'),
     
     # OS name mappings
     ('posix', 'unix'),